1. Field of the Invention
This invention relates to a power screwdriver mainly for use in attaching wooden material to a metal plate or panel by screws, and more particularly to a power screw feeder driver capable of successively driving screws which are fed in the form of a screw chain carrying a multiplicity of screws on a connecting strip.
2. Description of the Prior Art
In the construction of tall buildings including fifty stories or higher skyscrapers, iron or other metallic structural materials are used in various places and for diversified purposes, including room partitions, window frames etc. In order to facilitate attachment of curtains or other interior furnishings, wooden wall panels or sheets are usually fixed to iron sheets or frames so that one can easily drive nails or wood screws at desired positions on a wall or interior surface.
For attaching a wooden sheet to an iron structure, it has been the conventional procedure to provide female screws in the iron structure beforehand and to drive bolts into the female screws through holes which are formed in the wooden sheet. This wood mounting operation including the tapping of female screws in iron structures and formation of mounting holes in wooden sheets or other material is extremely troublesome particularly in case of a large or tall building which contains a great number of rooms.
In this connection, there have been developed very strong steel screws which are shaped like wood screws and have properties of directly tapping an iron sheet of several millimeters in thickness when driven under pressure by a screw driving tool which is engaged with a groove in the screw head. Accordingly, it has become possible to fix a wooden material to an iron sheet or similar structural material simply by driving screws into the wooden material which is placed on the iron sheet. There has also been known in the art the so-called screw feeder driver which can successively drive screws of this sort, for example, from U.S. Pat. No. 3,930,297, German Ouslegungsschrift No. 2,641,828 and Japanese Publication of Patent Application No. 57-33973.
The above-mentioned prior art screw feeder drivers utilize the construction of the conventional power screw-driver as it is, with a motor power transmission mechanism, a screw feed mechanism and a screw driver successively located forward of a heavy electric motor, so that it has a lengthy shape which is difficult to handle and has various drawbacks such as inclination of a screw being driven through wooden material and difficulty of feeding screws in the form of a continuous screw chain.